If you receive the TYPO3 error message "Parse error: Data structure could not be resolved to a valid structure." in the backend when attempting to edit a content element, it is worth taking a look at \typo3\sysext\core\Classes\Configuration\FlexForm\FlexFormTools.php.
The message above is displayed as soon as the variable
$dataStructure
is not of type Array. Since the $dataStructure variable is first parsed in the function
parseDataStructureByIdentifier()
it is helpful to generate test output at various points in the process (for example, echo $dataStructure). In our example, we were trying to parse an element of the Faceted Search extension (ke_search). The process accessed an XML file, specifically:
\typo3conf\ext\ke_search\pi2\flexform_pi2.xml
And this was where the error was located: the XML structure was invalid. After correcting the XML structure, everything worked smoothly again. Tested with TYPO3 8.7.1.
